Image forming apparatus, sheet feeding method

ABSTRACT

The present invention provides an image forming apparatus, a sheet feeding method, and a sheet feeding program that can prevent adverse effect brought about when the temporary stop position of a sheet deviates from a predetermined stop position. The present invention provides an image forming apparatus which includes a drive control unit  101  that controls the operation of driving feeding rollers for feeding sheets to a regist roller that performs skew correction for sheets being fed, and a retention state information take-in unit  102  that takes in information concerning the retention state of a sheet that is retained by the feeding rollers to be made to stand by temporarily, wherein the drive control unit  101  resumes the sheet feeding by the feeding rollers under predetermined timing based on information concerning the retention state of a sheet that is taken in by the retention state information take-in unit  102.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an image forming apparatus and a sheetfeeding method.

2. Description of the Related Art

Conventionally, in an image forming apparatus, skew correction andtiming adjustment (or so-called aligning) for sheets being fed arecarried out by a regist roller, etc. (refer to Jpn. Pat. Appln.Laid-Open Publication No. 11-184191). FIG. 6 shows a cross-sectionalview indicative of the entire configuration of a conventional imageforming apparatus.

In the image forming apparatus shown in FIG. 6, the following processingis performed. Firstly, sheets stocked in cassettes 31, 32, 33, 34 arepicked up by pickup rollers 31 b, 32 b, 33 b, 34 b. Then, thus picked upsheets are separated to respective papers one by one by sheet supplyrollers 31 a, 32 a, 33 a, 34 a and separation rollers 31 c, 32 c, 33 c,34 c to be supplied to a sheet feeding path 35. Sheets fed to the sheetfeeding path 35 are carried forward right before an intermediate feedingroller 38 by feeding rollers 36 a to 36 d. The intermediate feedingroller 38 is provided with a function of guiding sheets fed by an ADU(Automatic Duplexing Unit) 5, to be described later, or sheets fed alongthe sheet feeding path 35 to a regist roller 37 for performing skewcorrection and timing adjustment for sheets.

After undergoing skew correction and timing adjustment, toner imagesformed on the photosensitive surface of a photoconductor drum 20 aretranscribed to sheets guided to the regist roller 37 through theintermediate feeding roller 38. Toner images transcribed to the sheetsare fixed on the sheets by a fixing section 24. Sheets having imagesfixed thereon are directly discharged to the outside of the imageforming apparatus in case of one-side printing, and are guided to areverse feeding path 28 in case of duplex printing or in case sheetsthat have undergone one-side printing are discharged after beingreversed.

In case of duplex printing, sheets directed to the reverse feeding path28 are made to switchback to be fed by reverse rollers 29 and 30 to besent to an ADU 5. Sheets sent to the ADU 5 are fed by feeding rollers 5a to 5 d, and are directed to the intermediate feeding roller 38 again.Then, image forming processing by the photoconductor drum 20 and fixingsection 24 are carried out for the other sides of sheets fed through theADU 5, realizing duplex printing for sheets.

FIG. 7 shows a view for explaining the sheet feeding right before theregist roller 37, which is an enlarged view of part enclosed by a dottedline in FIG. 6.

As shown in FIG. 7, in the image forming apparatus of above-describedconfiguration, in case of performing image forming processing for aplurality of sheets consecutively, that is, in case of feeding aplurality of sheets to the regist roller 37 sequentially, when apreceding sheet P1 is aligned by the regist roller 37, a succeedingsheet P2 is made to stand by temporarily at a predetermined position Sright before the intermediate feeding roller 38 until a start command isissued. Similarly, a sheet fed to the regist roller 37 again through theADU 5 is made to stand by temporarily at a predetermined position rightbefore the intermediate feeding roller 38.

In case of performing image forming processing for sheets supplied fromthe plural cassettes 31 to 34 arranged on different positions on thesheet feeding route, the route on which sheets are fed toabove-described predetermined position varies depending on the positionof the cassettes 31 to 34. This means that, in case the cassette forsupplying sheets is different, the feeding roller (including the sheetsupply roller) through which sheets are fed varies.

Generally, under the environment of high temperature and high humidity,oil infiltrated to a bush of a bearing of a feeding roller (especially,a feeding roller using a clutch for transmitting driving force) is proneto steep, which reduces the rotation load of the feeding roller. Thisreduction of the rotation load leads to deterioration of the brakingperformance for sheets by a feeding roller, that is, when making a sheetstand by temporarily at above-described predetermined position,sometimes the sheet undesirably overruns the predetermined position(refer to a stop position S′ of the sheet P2 shown by a dotted line inFIG. 7). Furthermore, the braking performance to make a sheet stop atthe temporary standby position depends on the number of rollers whichapply braking force to the sheet.

In case there is raised a deviance (overrun) at the temporary standbyposition (temporary stop position) of a sheet, when the operation offeeding a sheet that is made to stand by temporarily is resumed, thesheet arrives at the regist roller 37 at the timing earlier than aregular timing. The misalignment in the arrival timing of a sheet to theregist roller 37 may undesirably lead to the malfunction of the registroller 37, which may become the cause of sheet jam due to fold of asheet.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to overcome theabove-mentioned drawbacks by providing an image forming apparatus, asheet feeding method, and a sheet feeding program that can preventadverse effect brought about when the temporary stop position of a sheetdeviates from a predetermined stop position.

According to the present invention, there is provided an image formingapparatus, including a drive control unit that controls the operation ofdriving feeding rollers for feeding sheets to a regist roller thatperforms skew correction for sheets being fed, and a retention stateinformation take-in unit that takes in information concerning theretention state of a sheet that is retained by the feeding rollers to bemade to stand by temporarily, wherein the drive control unit resumes thesheet feeding by the feeding rollers under predetermined timing based oninformation concerning the retention state of a sheet that is taken inby the retention state information take-in unit.

According to the present invention, there is also provided an imageforming apparatus, including a drive control unit that controls theoperation of driving feeding rollers for feeding sheets to a registroller that performs skew correction for sheets being fed, a retentionstate information take-in unit that takes in information concerning theretention state of a sheet that is retained by the feeding rollers to bemade to stand by temporarily, and an environment detection unit thatdetects at least one of the temperature and humidity, wherein, in caseat least one of the temperature and humidity detected by the environmentdetection unit goes beyond a predetermined threshold value, the drivecontrol unit resumes the sheet feeding by the feeding rollers underpredetermined timing based on information concerning the retention stateof a sheet that is taken in by the retention state information take-inunit.

According to the present invention, there is also provided a sheetfeeding method, including a drive control step that controls theoperation of driving feeding rollers for feeding sheets to a registroller that performs skew correction for sheets being fed, and aretention state information take-in step that takes in informationconcerning the retention state of a sheet that is retained by thefeeding rollers to be made to stand by temporarily, wherein the drivecontrol step resumes the sheet feeding by the feeding rollers underpredetermined timing based on information concerning the retention stateof a sheet that is taken in by the retention state information take-instep.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a block diagram for explaining the image forming apparatusin the present embodiment;

FIG. 2 shows a flow chart for explaining the sheet feeding method in thepresent embodiment;

FIG. 3 shows a flow chart for explaining detailed processing of thesheet feeding method in the present embodiment;

FIG. 4 shows a flow chart for explaining detailed processing of thesheet feeding method in the present embodiment;

FIG. 5 shows a timing chart indicative of drive timing of a registroller 37, an intermediate feeding roller 38, and feeding rollersexcluding the intermediate feeding roller 38 of the image formingapparatus in the embodiment;

FIG. 6 shows a cross-sectional view indicative of the entireconfiguration of a conventional image forming apparatus; and

FIG. 7 shows a view for explaining the sheet feeding right before aregist roller.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will further be described below with reference tothe accompanying drawings.

FIG. 1 shows a block diagram for explaining the image forming apparatusin the present embodiment. The basic configuration of the sheet feedingroute etc., within the image forming apparatus in the present embodimentis similar to that within the conventional image forming apparatus shownin FIG. 6 and FIG. 7. Therefore, parts or components similar to thoseshown in FIG. 6 and FIG. 7 are indicated with the same referencenumerals, and detailed explanation of which will be omitted.

The image forming apparatus in the present embodiment includes, inaddition to the configuration shown in FIG. 6, a drive control unit 101,a retention state information take-in unit 102, an environment detectionunit 103, a CPU 104, and a MEMORY 105.

The drive control unit 101 is provided with a function of controllingthe operation of driving feeding rollers (including the pickup rollers31 b to 34 b, sheet supply rollers 31 a to 34 a, separation rollers 31 cto 34 c, feeding rollers 36 a to 36 d, feeding rollers 5 a to 5 d shownin FIG. 6 in this embodiment) for feeding sheets to a regist roller thatperforms skew correction for sheets being fed.

The retention state information take-in unit 102 is provided with afunction of taking in information concerning the retention state of asheet that is retained by the feeding rollers to be made to stand bytemporarily. The information concerning the retention state includesinformation concerning the supply start position of the sheet to thefeeding route (cassette of which stage the sheet is supplied from,whether or not the sheet is sent through an ADU), and informationconcerning the size of the sheet (A4, A3, etc.).

The environment detection unit 103 includes a temperature sensor and ahumidity sensor, and detects at least one of the temperature andhumidity.

The CPU 104 is provided with a function of carrying out variousprocessing in the image forming apparatus, and is also provided with afunction of realizing various functions by executing programs stored inthe MEMORY 105. The MEMORY 105 may be a ROM, a RAM, etc., and isprovided with a function of storing various information and programs tobe utilized in the image forming apparatus.

The drive control unit 101 resumes the sheet feeding by the feedingrollers under predetermined timing based on information concerning theretention state of a sheet that is taken in by the retention stateinformation take-in unit 102 in case at least one of the temperature andhumidity detected by the environment detection unit 103 goes beyond apredetermined threshold value. Details of controlling the operation ofdriving the feeding rollers by the drive control unit 101 will beexplained later.

FIG. 2 shows a flow chart for explaining the sheet feeding method in thepresent embodiment.

The drive control unit 101 controls the operation of driving feedingrollers for feeding sheets to a regist roller that performs skewcorrection for sheets being fed (drive control step) (S801).

The retention state information take-in unit 102 takes in informationconcerning the retention state (information concerning the supply startposition of a sheet to the feeding route and information concerning thesize of a sheet) of a sheet that is retained by the feeding rollers tobe made to stand by temporarily (retention state information take-instep) (S802).

The environment detection unit 103 detects at least one of thetemperature and humidity (environment detection step) (S803). Any of theretention state information take-in step (S802) and the environmentdetection step (S803) can be performed first so long as both the stepsare performed prior to drive control step (S804) to be described later.

The drive control unit 101 resumes the sheet feeding by the feedingrollers under predetermined timing based on information concerning theretention state of a sheet that is taken in by the retention stateinformation take-in step in case at least one of the temperature andhumidity detected by the environment detection step goes beyond apredetermined threshold value (drive control step) (S804). On the otherhand, the processing is not restricted to this, and the operation offeeding a sheet can be resumed under above-described predeterminedtiming regardless of the temperature and humidity.

In the drive control step, when resuming the sheet feeding by thefeeding rollers under predetermined timing based on informationconcerning the retention state of a sheet that is taken in by theretention state information take-in step, it is desired that thepredetermined timing be delayed in case the number of feeding rollerswhich retain a sheet in the temporary standby state is small.

Generally, in case of temporarily stopping a sheet being fed, it isconsidered that the larger the number of feeding rollers which retain asheet in the temporary stop state is, the larger the braking forcebecomes. Accordingly, it is presumed that the smaller the number offeeding rollers which retain a sheet in the temporary stop state is (thesmaller the braking force is), the larger the value overrunning apredetermined temporary stop position S becomes. Thus, it becomespossible to make the leading edge of a sheet arrive at the regist rollerunder the regular timing by delaying the timing of resuming the sheetfeeding from the temporary standby state.

Furthermore, in case the posterior edge of a sheet is retained by sheetsupply rollers and separation rollers whose retention torque is large inthe temporary stop state (it is presumed from the sheet size and acassette for supplying sheet), it is considered that the sheet rarelyoverruns the predetermined temporary stop position. Accordingly, in thiscase, it is not necessary to delay the timing of resuming the sheetfeeding from the temporary standby state.

In addition, in the drive control step, when resuming the sheet feedingby the feeding rollers under predetermined timing based on informationconcerning the retention state of a sheet that is taken in by theretention state information take-in step, the predetermined timing canbe delayed by a period of time longer than 0 msec and shorter than 60msec from a predetermined reference timing in case the number of feedingrollers which retain a sheet in the temporary standby state is smallerthan a predetermined number of rollers.

Furthermore, in case the size of a sheet in the temporary standby stateis large (for example, A3 size), it is presumed that the number offeeding rollers which retain the sheet becomes necessarily large.Accordingly, the timing of resuming the sheet feeding is not made todelay from the predetermined reference timing (predetermined timing thatcan keep a suitable spacing between the leading edge of a sheet to befed again and the posterior edge of a preceding sheet). On the otherhand, in case the size of a sheet in the temporary standby state issmall (for example, letter size), it is presumed that the number offeeding rollers which retain the sheet becomes necessarily small.Accordingly, the timing of resuming the sheet feeding is made to delayfrom the predetermined reference timing.

Moreover, in case the size of a sheet in the temporary standby state islarge to some extent (for example, B4 size), and in case a cassette forsupplying sheet is a lowermost cassette 34 that makes the sheet feedingdistance to an intermediate feeding roller 38 long, the possibility thatthe pickup roller 34 b and the sheet supply roller 34 a whose brakingforce is large are in contact with the posterior edge of the sheet ispresumed to be low. Accordingly, the timing of resuming the sheetfeeding may be made to delay from the predetermined reference timing.

The intermediate feeding roller 38 of the image forming apparatus in theembodiment can feed sheets with speeds of at least three kinds or more.In this embodiment, the intermediate feeding roller 38 can be drivenwith a sheet supply speed, a process speed, and a duplex printing speed(referred to as ADU speed hereinafter).

Specifically, the sheet supply speed is a speed (for example, 420mm/sec) at the time of feeding sheets from the cassettes to the registroller, and the process speed is a speed (for example, 340 mm/sec) atthe time when toner images are transcribed to sheets from aphotoconductor drum 20, and the ADU speed is a speed (for example, 385mm/sec) when sheets are fed from an ADU 5 to the intermediate feedingroller 38. In recent years, since it is desired that the sheet feedingefficiency and printing efficiency be improved, the sheet feeding speedis becoming high. Thus, in case of temporarily stopping sheets at thepredetermined temporary stop position S, when the sheet feeding speed ishigh, overruns are prone to be raised frequently.

Accordingly, in case the sheet feeding speed right before beingtemporarily stopped is high, the possibility that sheets overrun thepredetermined temporary stop position S is presumed to be high, and thetiming of resuming the sheet feeding is made to delay. On the otherhand, in case the sheet feeding speed right before being temporarilystopped is low, the possibility that sheets overrun the predeterminedtemporary stop position S is presumed to be extremely low, and theoperation of feeding a sheet may be resumed under the predeterminedreference timing.

Specifically, feeding rollers which resume the sheet feeding in thetemporary standby state mean rollers including at least one of thefeeding rollers 36 a to 36 d, pickup rollers 31 b to 34 b, and sheetsupply rollers 31 a to 34 a. The number of feeding rollers which resumethe sheet feeding may be increased or decreased according to need. Forexample, optimum sheet feeding can be realized by also changing thetiming of resuming the sheet feeding using the feeding roller 36 d inaddition to only controlling the timing of resuming the sheet feedingusing the feeding roller 36 a.

As for the timing of resuming the sheet feeding, depending on thedifference of the sheet supply speed and the process speed, for example,in case the sheet supply speed is 420 mm/sec and the process speed is340 mm/sec, feeding a sheet is restarted when 100 msec elapses after aregist roller 37 is driven (corresponding to the predetermined referencetiming) in case a sheet is fed from cassettes 31 and 32 or thetemperature and humidity are in the ordinary state, while the restarttiming of feeding a sheet is desired to be staggered by 30 msec fromabove-described reference timing in case a sheet is fed from cassettes33 and 34.

The timing of resuming the sheet feeding can be changed by 10 msec unitusing an adjustment code through an operation input unit, not shown, bya service personnel etc. In this case, information concerning thuschanged restart timing can be stored in a storage area of the MEMORY 105or an external equipment. Accordingly, the timing of resuming the sheetfeeding can be set to an optimum value depending on the environment foruse, configuration of device, etc.

FIG. 3 and FIG. 4 show flow charts for explaining detailed processing ofthe sheet feeding method in the present embodiment.

When image forming processing is started, the environment detection unit103 takes in temperature data (S101).

In case thus taken in temperature is higher than predeterminedtemperature threshold value Tbase (° C.) (S102, No), the drive controlunit 101 reduces feeding time Ttr1 in feeding a sheet to the temporarystop position S using the feeding rollers by α tr1 (msec), or delaystiming Tw to resume the operation of feeding a sheet in the temporarystop state by α w (msec) (S103).

Next, the environment detection unit 103 takes in humidity data (S104).

In case thus taken in humidity is higher than predetermined humiditythreshold value Tbase (%) (S105, No), the drive control unit 101 reducesfeeding time Ttr1 in feeding a sheet to the temporary stop position Susing the feeding rollers by β tr1 (msec), or delays timing Tw to resumethe operation of feeding a sheet in the temporary stop state by β w(msec) (S106).

The drive control unit 101 makes the sheet feeding be performed withthus corrected sheet feeding time before temporary stop under therestart timing of feeding a sheet after temporary stop.

Next, the processing of resuming the sheet feeding will be explainedusing a flow chart shown in FIG. 4.

When aligning processing by the regist roller 37 is completed and sheetfeeding by the regist roller 37 is started, the drive control unit 101determines which cassette a sheet that is made to temporarily stop rightbefore the intermediate feeding roller 38 is fed from (S201, S203,S205), and selects the timing of resuming the sheet feeding set upcorresponding to the respective cassettes (S202, S204, S206, S207).

Then, the drive control unit 101 makes the sheet feeding by the feedingrollers stand by until the restart timing of feeding a sheet (timingdelayed by Tw from the predetermined reference timing) selected inabove-described step (S208), and resumes the operation of feeding asheet in the temporary standby state (S209). In this embodiment, therestart timing is determined in S103, S106 shown in FIG. 3, and S202,S204, S206, S207 shown in FIG. 4.

In the present embodiment, the respective steps of the processing in thesheet feeding method are realized by making the CPU 104 execute a sheetfeeding program stored in the MEMORY 105.

FIG. 5 shows a timing chart indicative of drive timing of the registroller 37, intermediate feeding roller 38, and feeding rollers excludingthe intermediate feeding roller 38 of the image forming apparatus in theembodiment.

A sheet that is fed from a cassette is carried forward to the registroller 37 by the intermediate feeding roller 38 with the sheet supplyspeed of 420 mm/sec. Then, the sheet has its leading edge applied to anip portion of the stopped regist roller 37 to be aligned. Afterward,the intermediate feeding roller 38 and the regist roller 37 feed thesheet with the process speed of 340 mm/sec.

Then, a succeeding sheet that is made to stand by to form an image onone side thereof is carried forward to the regist roller 37 by theintermediate feeding roller 38 with the sheet supply speed of 420mm/sec. FIG. 5 shows the state in which the timing to resume the sheetfeeding by the feeding rollers (which correspond to a feed clutch 1 anda feed clutch 2 for transmitting motive energy to the feeding rollers,in this embodiment) is delayed by Tw.

In case image forming processing for one sheet side is performed forthree sheets (in FIG. 5, first sheet is omitted), a sheet having animage formed on one side thereof is reversed to be carried forward, andis fed with an increased speed after switchback, and, after the speed islowered right before the ADU 5, is carried forward to the regist roller37 with the ADU speed of 385 mm/sec, to form an image on the other sidethereof having formed thereon no image.

In above-described embodiment, the function for implementing the presentinvention is stored inside an image forming apparatus in advance. On theother hand, the present invention is not restricted to this, that is,similar function may be downloaded to an image forming apparatus from anetwork, or a recording medium having stored therein similar functionmay be installed to an image forming apparatus. The recording medium maybe of any figuration such as a CD-ROM so long as the recording mediumcan store programs and can be read out by an image forming apparatus.Furthermore, function obtained by previously performed installing anddownloading may be realized cooperatively with the OS (operating system)in an image forming apparatus.

As in the above, according to the present embodiment, stable sheetfeeding in view of factors bringing about variation of the temporarystop position of sheets such as cassette stage, oil of a bush, load offeeding rollers can be realized under the environment of hightemperature and high humidity.

While the invention has been described in accordance with certainpreferred embodiments in detail, it should be understood by thoseordinarily skilled in the art that the invention is not limited to theembodiments, but various modifications, alternative constructions orequivalents can be implemented without departing from the scope andspirit of the present invention.

According to the present invention, it becomes possible to provide animage forming apparatus, a sheet feeding method, and a sheet feedingprogram that can prevent adverse effect brought about when the temporarystop position of a sheet deviates from a predetermined stop position.

1. An image forming apparatus, comprising: a drive control unit thatcontrols the operation of driving feeding rollers for feeding sheets toa regist roller that performs skew correction for sheets being fed; anda retention state information take-in unit that takes in informationconcerning the retention state of a sheet that is retained by thefeeding rollers to be made to stand by temporarily, wherein the drivecontrol unit resumes the sheet feeding by the feeding rollers underpredetermined timing based on information concerning the retention stateof a sheet that is taken in by the retention state information take-inunit.
 2. An image forming apparatus, comprising: a drive control unitthat controls the operation of driving feeding rollers for feedingsheets to a regist roller that performs skew correction for sheets beingfed; a retention state information take-in unit that takes ininformation concerning the retention state of a sheet that is retainedby the feeding rollers to be made to stand by temporarily; and anenvironment detection unit that detects at least one of the temperatureand humidity, wherein, in case at least one of the temperature andhumidity detected by the environment detection unit goes beyond apredetermined threshold value, the drive control unit resumes the sheetfeeding by the feeding rollers under predetermined timing based oninformation concerning the retention state of a sheet that is taken inby the retention state information take-in unit.
 3. The image formingapparatus according to claim 1, wherein the retention state informationtake-in unit takes in information concerning the supply start positionof the sheet to the feeding route.
 4. The image forming apparatusaccording to claim 1, wherein the retention state information take-inunit takes in information concerning the supply start position of thesheet to the feeding route, and information concerning the size of thesheet.
 5. The image forming apparatus according to claim 1, wherein,when resuming the sheet feeding by the feeding rollers underpredetermined timing based on information concerning the retention stateof a sheet that is taken in by the retention state information take-inunit, the drive control unit delays the predetermined timing in case thenumber of feeding rollers which retain a sheet in the temporary standbystate is small.
 6. The image forming apparatus according to claim 1,wherein, when resuming the sheet feeding by the feeding rollers underpredetermined timing based on information concerning the retention stateof a sheet that is taken in by the retention state information take-inunit, the drive control unit delays the predetermined timing by a periodof time longer than 0 msec and shorter than 60 msec from a predeterminedreference timing in case the number of feeding rollers which retain asheet in the temporary standby state is smaller than a predeterminednumber of rollers.
 7. A sheet feeding method, comprising: a drivecontrol step that controls the operation of driving feeding rollers forfeeding sheets to a regist roller that performs skew correction forsheets being fed; and a retention state information take-in step thattakes in information concerning the retention state of a sheet that isretained by the feeding rollers to be made to stand by temporarily,wherein the drive control step resumes the sheet feeding by the feedingrollers under predetermined timing based on information concerning theretention state of a sheet that is taken in by the retention stateinformation take-in step.
 8. The sheet feeding method according to claim7, further comprising: an environment detection step that detects atleast one of the temperature and humidity, wherein, in case at least oneof the temperature and humidity detected by the environment detectionstep goes beyond a predetermined threshold value, the drive control stepresumes the sheet feeding by the feeding rollers under predeterminedtiming based on information concerning the retention state of a sheetthat is taken in by the retention state information take-in step.
 9. Thesheet feeding method according to claim 7, wherein the retention stateinformation take-in step takes in information concerning the supplystart position of the sheet to the feeding route.
 10. The sheet feedingmethod according to claim 7, wherein the retention state informationtake-in step takes in information concerning the supply start positionof the sheet to the feeding route, and information concerning the sizeof the sheet.
 11. The sheet feeding method according to claim 7,wherein, when resuming the sheet feeding by the feeding rollers underpredetermined timing based on information concerning the retention stateof a sheet that is taken in by the retention state information take-instep, the drive control step delays the predetermined timing in case thenumber of feeding rollers which retain a sheet in the temporary standbystate is small.
 12. The sheet feeding method according to claim 7,wherein, when resuming the sheet feeding by the feeding rollers underpredetermined timing based on information concerning the retention stateof a sheet that is taken in by the retention state information take-instep, the drive control step delays the predetermined timing by a periodof time longer than 0 msec and shorter than 60 msec from a predeterminedreference timing in case the number of feeding rollers which retain asheet in the temporary standby state is smaller than a predeterminednumber of rollers.